When the requirements for the P-40 were formulated, no prospect of high-altitude enemy attack against the U.S.A was envisaged, so that coastal defence and ground attack were the main tasks indicated.

Low-altitude flying qualities and rugged construction therefore received priority, and, in fact, the P-40 was subsequently to prove itself an excellent ground-attack weapon. But at the time of the Japanese attack on pearl Harbour this fighter was already approaching obsolescence, despite having been in production for less than two years.

Nevertheless, between 1940 and 1944, when acceptances were terminated, a total of 13,738 P-40 fighters were delivered to the U.S.A.A.F., the peak number in service being 2,499 in April 1944.

The P-40 was a relatively clean design, and was unusual for its time in having a fully retractable tail-wheel. One hundred and ninety-seven P-40s were built in 1939-40 for the U.S.A.A.F., and many more were sold abroad to Britain and France. In the R.A.F., which service purchased 140 outright, it was knows as the Tomahawk MK.I, IA, and IB.